Hi EarthGrl,
I think what you have there is actually a Satin Pothos...
Satin Pothos (Scindapsus pictus 'Argyraeus')
I don't have the Satin...(wish I did. It's a beauty!)
But If I'm not mistaken, they really prefer excellent drainage, and to dry slightly between thorough waterings. Does the pot have drain holes? Have you re potted?
The link that I added also states partial to dappled shade. It may help if you open the shade. What exposure is the window facing?
My guess would be too much water, and not enough light.
Others (I hope) will also chime in soon...
edited to say... I just realized that Silver Philodendron IS another common name for this plant...sorry....